The present invention relates to current conducting brushes in general, and more particularly to improvements in brush holder assemblies for use in electric machines such as d-c motors, a-c motors and generators. Still more particularly, the invention relates to improvements in assemblies of the type wherein one or more brushes are movably mounted in carriers or clips which are separably affixed to a ring-shaped holder made of an insulating material. Such brushes can be used to supply current to or to receive current from a commutator or a slip ring, depending on the nature of the electric machine.
In heretofore known brush holder assemblies, the brushes are mounted on bridge-like holders which maintain them in contact with the rotating part or parts of the electric machine, such as a motor or a generator. The conventional bridge-like holders include at least one ring which is adjacent to a slip ring or to a commutator and supports a carrier wherein an adjustable brush is mounted in such a way that it can bear against the periphery of the rotating part of the machine in order to establish the required electrical connection. The just described brush holder assemblies are especially popular in relatively small machines, i.e., when the diameter of the aforementioned ring-shaped holder is relatively small. Such brush holder assemblies are used less frequently or not at all if the diameter of the commutator is rather large. Regardless of their intended or actual use, conventional brush holder assemblies of the above outlined character exhibit the drawback that they must be furnished in a large number of different sizes and shapes, one for each of a wide variety of differently dimensioned commutators or slip rings. In addition, it is necessary to provide a large number of differently dimensioned and/or configurated ring-shaped holders to accept differently configurated and/or dimensioned brush carriers. The various parts of such conventional assemblies must be manufactured in specially designed machines and by resorting to specially designed tools so that they can be produced at a reasonable cost only in large or extremely large numbers.
Attempts to overcome the drawbacks of the above outlined conventional brush holder assemblies include the provision of substantially straight ruler-shaped arms each of which supports a battery of brushes so that a selected brush of each battery can be used in conjunction with a particular commutator or with a particular slip ring. Thus, each brush of each battery of brushes is disposed at a different radial or axial distance from the ring-shaped holder for the carriers. The utilization of straight arms with batteries of brushes thereon enhances the versatility of the brush holder assemblies but it also contributes to the cost because the positions of brushes in each of the batteries must be selected and maintained with a very high degree of accuracy. Moreover, elongated arms which support the batteries of brushes are prone to vibration in response to vibration of the respective machine and this affects the flow of current between the selected brushes and the rotary part or parts which are in contact with the brushes.